Hot-gas piston apparatus having cylinder means and axially arranged piston bodies, heat exchangers, and regenerator therein



y 6, 1952 w. H. STIGTER ,0

HOT-GAS PISTQN APPARATUS HAVING CYLINDER MEANS AND AXIAL-LY ARRANGED PISTON BODIES, HEAT EXCHANGERS, AND REGENERATOR THEREIN Filed April 30, 1946 IN V EN TOR.

AGENT Patented May 6, 1952 HOT-GAS PISTON APPARATUS HAVING CYL- INDER MEANS AND AXIALLY ARRANGED PISTON BODIES, HEAT EXCHANGERS, AND REGENERATOR THEREIN Willem Hendrik Stigter, Eindhoven, Netherlands, assignor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford,

Conn., as trustee Application April 30, 1946, Serial No. 666,098 In the Netherlands December 3, 1945 4 Claims. I 1

The present invention relates to hot-gas enines of the reciprocatory piston type.

In such hot-gas engines it is the practice to cause the volume of the caloric cycle or working medium present in the engine to vary by means of two piston-like bodies. One of these bodies,

usually referred to as the displacer, is operative as such by means of both end surfaces thereof. On the other hand, the other piston-like body participates in the volume varying process only by means of the end thereof remote from the crank mechanism of the engine. The two chambers which contain the gaseous working medium which have the volume thereof varied to so participate in-the caloric cycle, are in permanent communication with each other. This is accomplished, as a rule, bymeans of a communication space or communication canals that are grouped about the space in which the two piston-like bodies move. A disadvantage of this arrangement is that the clearance of such an engine is comparatively large and hence affects the output of the engine per unit of volume. I

The present invention provides means operative to remove this difficulty as will be pointed out hereinafter.

In hot-gas piston apparatus (i. e. either hotgas engines or refrigerating machines operating on the reverse hot-gas engine principle), constructed according to the invention, the volume of the caloric cycle or working medium present in the apparatus is varied by the adjacent end surfaces of two axially arranged piston-like bodies. Such construction then allows arranging the heat exchangers, and in some cases a regenerator, in the apparatus space between the two piston-like bodies. This in time results in that the clearance in such apparatus can be maintained small, while the flow losses are reduced to a minimum. The last optimum result is due to the fact that the course of the flow of gas is perfectly linear. In other words, neither any bends nor any auxiliary canals are traversed by the gas.

In accordance with a preferred embodiment of the invention, the piston-like body which is remote from the crank mechanism of the engine, has the end thereof most remote from said drive. vary the volume of an enclosure sealed from the surroundings. It is then possible to introduce a gas into this enclosure and to choose the compression ratio in this space to be such that the course of the torque or of a bearing load of the apparatus becomes more favorable.

In order that the invention may be clearly understood and readily carried into effect, it will accompanying drawing, in which:'

Figure 1 is a longitudinal section of a hot-gas piston apparatus constructed in accordance with the invention and, in this case, as a hot-gas engine; and

Figure 2 is a cross-sectional view of the heater of the apparatus shown in Figure 1 and taken on the line II-II thereof. v

The engine according to the invention comprises an engine housing in turn comprising three sections I, 2 and 3 of a cylinder mounted on a crankcase 4, all of which are assembled by means of flanges as shown. A piston-like body 5 is adapted to move in the section I, while a pistonlike body 6 is adapted to move in the section 3. The end surface I of the piston 5 and the end surface 8 of the piston 6 jointly influence the volume of the gas which participates in the caloric cycle of the engine. For this purpose, as is the practice in hot-gas engines, the movement of the piston-like body 5, which influences the volume of the hot space 9, reciprocates out of phase with respect to the reciprocation of the piston-like body 6, which varies the volume of the cold space H]. The out-of-phase relationship or phase difierence may be of the order of for example. This phase difference is conventionally obtained by a crank mechanism which in this case comprises a piston rod l l which is attached to piston body 5 and which extends through the piston body 6. The piston rod H is coupled by means of a connecting rod I2 to a crank 13 on a crankshaft I 4. Numerals I5 and i5 designate pivot points in the connections between the piston rod I l and connecting rod I2 on the one hand, and between connecting rod 12 and the crankshaft I4 on the other. The piston-like body 6 has a piston rod assembly I! connected thereto, which is constructed so as to be double and in V-shape, as shown, and lies in front and at theback of the piston rod I l. The piston rodassembly I1 is coupled by means of a connecting'rod l8 to a crank IS on the crankshaft Hi. The pivot points in this connection are designated 20 and and 2|. It is also possible that the piston 8 may be constructed as a trunk piston, the connecting.

rod l8 then engaging pivot points on the piston 6 itself.

The hot space 9 and thecold space [0 are in permanent communication via the heat exchangers 22 and 23 and the regenerator 24. The gas or working medium in the engine absorbs heat supplied to it via the heat exchanger 22. The heat to be applied in turn to the heat exchanger 22 is diagrammatically indicated by the arrows 25. As may be seen in Figure 2, the heat exchanger 22 is assumed in this case to comprise a plurality of radial fins which arev placed both 7 on the inside and on the outside of the wall of part 20 withdraw heat from theworking medium in the engine and transmit it through the wall of the housing to the fins on the outside of the housing, which are cooled in somesuitablemanner. Thi may be done, for example, byair flowing past the outer fins or by a cooling liquid.

This causes heat to be dissipated on the outside of the engine, as is denoted diagrammatically by the arrows 25. I The fins of the heat exchangers 22 and 23thatare external to the housing parts -2a and 2c are heatinsulated from each other by apartition 21. In addition, precautions have to be taken to prevent heat supplied to the engine as indicated by. the arrows 25, from flowing through'the material of the wall .of the housing part 2a to the heat exchanger-.23.. Thismay be efiected, for. example, by making the partZb of the engine housing between the two heat exchangers of material of poor thermalconductivity, as indicated in Fig. l. Asa matter of course, the aforesaid detrimental heat flow may be prevented otherwise, for example, by the use ofmore complicated constructions of the heat exchangers.

Inorder to raise the output or" the engine, a regenerator 2A is provided between the two heat exchangers 22 and .253; Such regenerator 24 may be made, for example, of very thin wire-like material..

If, as has been assumed, the apparatus operates asa hot-gas engine, the heat exchanger 22 is maintained at a temperature of 706 C., and the temperature of-the heat exchanger 23 is maintained, for example, at 30 C. The crankshaft it of the engine consequently supplies mechanical energy. If in contradistincticn to this, the apparatus is designed as a refrigerating. machine operatingon the reverse hot-gas engine principle, the heat exchanger 22 is maintained by the outsidemedium to be cooled at a temperature of say 20 C., and the heat withdrawn from the outside medium to be cooled is transmitted to the outside at a temperature of say +20 C. by'the I heat exchanger 23. In this case, the apparatus consequently supplies caloric energy (Le. it supplies cold at the area ofthe heat exchanger 22'). Infthis case, the crankshaft It must be actuated in some manner. 7 7

By causing the most remote end 28 "ofthe 7 piston which is located remote from the crank mechanism of the apparatus, to move intothe enclosed space 29; sealed from the surroundings, at a properly chosen compression of the gas contained inthe saidenclosed space the course of the torque or of a bearing load in the operating apparatus may bemade'more favorable-.=

' What I claim is:

A hot-gas piston apparatus comprising "ially arranged piston-bodies reciprocably" confined by the inner periphery of said substantially im- 4 V perforate wall section therein, said piston bodies completely enclosing the volume of the working medium of the caloric cycle in said cylinder means by the. adjacentend surfa'cesof saidpiston bodies and said inner periphery of said substantially imperforate wall section, and means for reciprocating said piston bodies out of phase in relation to eachother whereby the volume of the working medium is varied during operation of the apparatus.

2. A hot-gas .piston apparatus comprising cylinder means and two axially arranged piston bodiestherein enclosing the volume of the working medium of the caloric cycle in said cylinder means by the adjacent end surfaces of said piston bodies, heat exchanger means and a regenerator enclosed in the space between said piston bodies, and means for reciprocating said piston bodies out of phase in relation to each other whereby the volume of the working medium is varied during operation of the apparatus.

3. A hot-gas piston apparatu comprising cylinder means, said. cylinder means comprising a substantially imperforate wall section, .two axially arranged piston bodies reciprocably confined by the inner periphery of said substantially imperforate wall section, therein, .said piston bodies completely enclosing the volume of the working medium of the caloric cycle in said oylinder means by the. adjacent end surfaces of saidpiston bodies and vsaidinner periphery of' substantially imperforate wall section,imeans for reciprocating said piston .bodies out ofipha'se in relation to eachother. whereby the. volume of the working medium is varied during operation of the apparatus, and said eyiinderimeans lcomprising a closure member fixed atone. end thereof, said closure member being positioned .opposits the end surface of .one of said piston bodies other than said adjacent end surface for ,enclosing a second volume. whereby said .secondenclosedvolume i varied uponreciprocationi of one of said piston bodies.

4. A hot-gas piston apparatus comprising cylinder means and two axially arranged piston bodies therein enclosing the volume of theworking medium of the caloric cycle inisaidlcylihder means by the adjacent end surfaces of said piston bodies, means for reciprocating-said piston bodies out of phase in relation; to each otherwhereby the volume of the working medium'isvaried during operation of. the apparatus, heat. exchanger means and. a regenerator enclosedinthe space between said piston bodies, and said. cylinder 5 means comprising a closure member fixed atone REFERENCES crash The following references are of,reeord.i-n..the file of this patent:

UN ITED STATES PATENTS Number 7 Name 7 Date- 2,465,139 van 'Weenen'et Mar-.22, 1949 FOREIGN PATENTS iiumlaerfl Country Dates-e 196,620 Great Britain Octr20; 1924 

